In the manufacture of corrugated paper cartons or boxes, rectangular corrugated sheets or blanks are first produced in a machine known as a corrugator. The sheets are then stacked for storage and handling purposes. They are subsequently individually processed through a printer or a die cutter that either imprints each sheet or forms carton blanks to the requirements of a customer.
Printing machines and die cutters operate at very high rates of speed. Simply loading successive vertical stacks of the corrugated sheets into an infeed hopper for such a machine is ineffective because of the amount of physical labor required to place each stack accurately within the hopper. The amount of labor required would result in an interruption of the operation of the machinery being fed or running the machine at a reduced rate of speed.
The present machine and method assure that a continuous supply of corrugated sheets is maintained within the infeed hopper of a printing machine or a die cutting machine while operating at a high rate of speed. This is accomplished by unstacking the corrugated sheets and pre-feeding them to the receiving hopper of the sheet processing machinery in a continuous shingled manner at a delivery rate that will not interrupt operation of the sheet processing machinery.
Where the incoming sheets or blanks are handled in very large stacks, it has been found advisable to design machines that initially divide each stack into a plurality of smaller "blocks" which are then successively handled and shingled along a longitudinal path leading to the blank processing machinery being fed. After being divided, each block might be inverted or simply deposited on a feed conveyor leading to a shingle gate.
The division of a large stack of corrugated sheets or blanks into several equally-sized blocks requires accurate separation between successive blocks. Because of the many variations that can occur in production of corrugated sheets, as well as frictional and static electricity forces that can interfere with separation of a stack, sliding successive blocks of such sheets from the top of a stack often results in a "trailing sheet" being dragged partially across the stack under the removed block. The protruding edges of the trailing sheet can jam the machinery and result in unwanted stoppage of the machinery. The present disclosure is primarily concerned with elimination of such trailing sheets at the bottom of a divided block.
The present disclosure attacks the problem of trailing sheets in two ways. (1) It provides frictional forces at the top of the remaining stack of sheets to impede sliding movement of the top sheet. The frictional forces are applied by means of a roller on the block pusher that initiates movement of each block from the top of a stack. (2) It also provides an improved ramp for initially lifting each block from the remaining sheets in the stack.